The present invention relates to a system for and a method of measuring a dynamic condition of a pneumatic tire and, more particularly to a system for and a method of determining at least one dynamic condition of a pneumatic tire by measuring the rotational angular position of the tire and/or a wheel or wheel carrier the tire is mounted on.
The present invention relates to monitoring of conditions of any rotary element, but is particularly concerned with the monitoring of conditions of wheels and pneumatic tires mounted on wheels. As a rotary element, a tire""s angular position, rotational (angular) velocity and acceleration, rate of change of acceleration, and revolution count are important in determining such things as vehicle and/or tire instantaneous position, speed, mileage, acceleration and braking, slip/skid, and are also factors in the wear of the tire. Certain of these elements are utilized in control of vehicle braking systems, such as automotive and aircraft ABS systems (anti-lock braking system). Existing monitoring systems generally assume the approximation that the tire/wheel assembly is rigid in the tangential direction (tangential to the direction of rotation, e.g., forward or backward relative to a rolling tire). The present invention moves beyond this rigid approximation in order to monitor other wheel and/or tire operating characteristics, such as for example, torque on the tire.
In addition to rotational/angular characteristics, other important characteristics to be monitored in a pneumatic tire are pneumatic pressure and temperature. Pressure (pneumatic pressure) is well known as a critical factor in pneumatic tire operation, most importantly if there is a loss of sufficient pressure to safely operate the tire, e.g., a xe2x80x9cflat tirexe2x80x9d. The (pneumatic) temperature is generally of secondary importance. Although it can be used to indicate an average temperature of the tire and wheel surrounding the pneumatic cavity, temperature is mostly used to normalize a pressure measured in a hot tire to a xe2x80x9ccold pressurexe2x80x9d value, i.e., the pressure as it would be in a xe2x80x9ccoldxe2x80x9d tire.
A great deal of prior art is devoted to apparatus and methods for measuring and monitoring rotary element and pneumatic conditions, particularly as they relate to pneumatic tire conditions.
THE ASSIGNEE""S ONGOING DEVELOPMENT EFFORTS
For a century, the Goodyear Tire and Rubber Company of Akron Ohio, assignee of the present invention, has been the uncontested industry leader in tire product technology. For example, as early as 1892, a puncture-resistant tire was patented. In 1934, a year recognized as the beginning of the run-flat era, Goodyear introduced the Lifeguard (tm) safety tube, a fabric tube within the tire, used commercially by automakers and on trucks. In 1993, Goodyear""s Eagle GS-C EMT (Extended Mobility Technology) Tire won the Discover Award for Automotive Technological Innovation. In 1996, the Goodyear Eagle F1 run-flat tire was chosen as standard equipment on the 1997 Chevrolet C-5 Corvette.
Other examples of the strides Goodyear has taken in the advancement of tire and related technologies include, but are not limited to, the following patented inventions:
Commonly-owned U.S. Pat. No. 3,665,387 (Enabnit; 1972), entitled SIGNALLING SYSTEM FOR LOW TIRE CONDITION ON A VEHICLE, incorporated in its entirety by reference herein, discloses a low tire pressure warning system adaptable for any number of wheels of a vehicle and providing dashboard indications of system operation and low pressure conditions while the vehicle is in motion.
Commonly-owned U.S. Pat. No. 3,831,161 (Enabnit; 1974), entitled FAIL-SAFE MONITORING APPARATUS, incorporated in its entirety by reference herein, discloses monitoring vehicle tire pressure wherein the operator is warned of an abnormal or unsafe condition of one or more of the tires.
Commonly-owned U.S. Pat. No. 3,872,424 (Enabnit; 1975), entitled APPARATUS AND METHOD FOR TRANSMITTING AUXILIARY SIGNALS ON EXISTING VEHICLE WIRING, incorporated in its entirety by reference herein, discloses communicating with low tire pressure monitoring circuits using power pulses carried on existing vehicle wiring (e.g., the turn signal circuits).
Commonly-owned U.S. Pat. No. 4,052,696 (Enabnit; 1977), entitled TIRE CONDITION MONITOR, incorporated in its entirety by reference herein, discloses a tire condition sensing circuit that includes a ferrite element that changes from a ferromagnetic to a non-ferromagnetic state in response to a temperature increase above the material Curie point.
Commonly-owned U.S. Pat. No. 4,099,157 (Enabnit; 1978), entitled SINGLE WIRE POWER/SIGNAL SYSTEM FOR VEHICLE AUXILIARY DEVICES, incorporated in its entirety by reference herein, discloses providing both power to and receiving detection signals from a remotely located condition monitoring device using a single wire with ground return through the vehicle frame.
Commonly-owned U.S. Pat. No. 4,911,217 (Dunn, et. al.; 1990), entitled INTEGRATED CIRCUIT TRANSPONDER IN A PNEUMATIC TIRE FOR TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses an RF transponder in a pneumatic tire. FIG. 1a of this patent illustrates a prior-art identification system (xe2x80x9creaderxe2x80x9d) that can be used to interrogate and power the transponder within the tire. The identification system includes a portable hand-held module having within it an exciter and associated circuitry for indicating to a user the numerical identification of the tire/transponder in response to an interrogation signal.
Commonly-owned U.S. Pat. No. 5,181,975 (Pollack, et. al.; 1993), entitled INTEGRATED CIRCUIT TRANSPONDER WITH COIL ANTENNA IN A PNEUMATIC TIRE FOR USE IN TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer. As described in this patent, in a tire that has already been manufactured, the transponder may be attached to an inner surface of the tire by means of a tire patch or other similar material or device.
Commonly-owned U.S. Pat. No. 5,218,861 (Brown, et al.; 1993), entitled PNEUMATIC TIRE HAVING AN INTEGRATED CIRCUIT TRANSPONDER AND PRESSURE TRANSDUCER, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer mounted within the pneumatic tire. Upon interrogation (polling) by an external RF signal provided by a xe2x80x9creaderxe2x80x9d, the transponder transmits tire identification and tire pressure data in digitally-coded form. The transponder is xe2x80x9cpassivexe2x80x9d in that it is not self-powered, but rather obtains its operating power from the externally-provided RF signal.
The commonly-owned U.S. Patents referenced immediately hereinabove are indicative of the long-standing, far-reaching and ongoing efforts being made by the Goodyear Tire and Rubber Company in advancing tire product technology, particularly in the area of monitoring tire operating conditions.
Dynamic Conditions
Dynamic conditions such as position and angular velocity of a rotary element are readily measured.
U.S. Pat. No. 3,831,570, incorporated in its entirety by reference herein, discloses measuring a crankshaft""s rotary position using a magnetic pickup coil, a rotating toothed wheel, and a permanent magnet. The toothed wheel has a number of teeth corresponding to the number of spark plugs.
U.S. Pat. No. 3,832,640, incorporated in its entirety by reference herein, discloses determining a large number of angular relationships (rotary positions) in a rotating element such as a crankshaft.
Straightforward tire revolution counters are well known, and are disclosed for example in U.S. Pat. Nos. 4,842,486 and 5,524,034, both of which are incorporated in their entirety by reference herein.
U.S. Pat. No. 5,218,862, incorporated in its entirety by reference herein, discloses a tire pressure monitor comprising wheel speed sensors located at the vehicle""s wheels to convey wheel speed information to an electronic controller. This patent notes that the wheel speed discrepancy between one tire to the others indicates the relative tire pressure, but that discrepancy may also be indicative of the vehicle turning, accelerating or decelerating, going up or down steep grades, or of one wheel slipping, or of a cross wind bearing on the vehicle.
U.S. Pat. No. 5,274,355, incorporated in its entirety by reference herein, discloses a system for monitoring pressure and temperature of rotating pneumatic tires. An elastic diaphragm is embedded in or bonded to the sidewall of the tire. Tire pressure changes cause measurable expansion and contraction of the diaphragm surface. The diaphragm comprises a pair of reflective stripes spaced apart from one another at a fixed distance to define a reference dimension, and another pair of reflective stripes which move relative to one another as the diaphragm expands or contracts in relation to the tire inflation pressure. The time interval between pulses associated with the reflective stripes, as sensed by photodetectors affixed to the vehicle indicates individual tire speed. The background infrared radiation naturally emitted from the tire indicates tire temperature.
U.S. Pat. No. 5,345,217, incorporated in its entirety by reference herein, discloses measuring wheel speed of a motor vehicle with a multi-tooth pulse generator on each wheel (as is used on electronic Anti-Lock Braking Systems) to produce a series of pulses spaced apart by equal increments of angular rotation of each wheel. The speed of each wheel is compared to the others, to determine if, and to what extent, a tire is deflated.
U.S. Pat. No. 5,569,848, incorporated in its entirety by reference herein, discloses a system for monitoring tire pressure, comprising toothed ring sensors affixed to each wheel assembly, a sensor operatively associated with each respective toothed ring and producing signals that are a measure of the rotational velocity of the wheels, and a computer receiving signals from the sensors. The computer monitors the wheel speed sensors during vehicle operation, calculating and indicating vehicle speed, distance traveled by the vehicle and low tire pressure.
U.S. Pat. No. 5,721,528, incorporated in its entirety by reference herein, discloses a low tire pressure warning system utilizing angular displacement sensors at each wheel. The system utilizes wheel displacement sensors already in place on vehicles that include ABS systems. Certain vehicle operating conditions, such as excessive or very low speeds, braking, and turns, are determined from the sensor outputs.
U.S. Pat. No. 3,588,814, incorporated in its entirety by reference herein, discloses an electric tire inflation indicator which determines the inflated condition of a tire by monitoring the rotational travel speed of the tire""s respective wheel, by means of a stationary reed switch and a magnet rotating with the wheel.
U.S. Pat. No. 5,749,984, incorporated in its entirety by reference herein, discloses a tire monitoring system and method utilizing a sensor in the tire to detect tire sidewall deflection and thereby determine tire pressure, tire speed and the number of tire revolutions.
Static Conditions
In addition to the aforementioned dynamic conditions (e.g., position, rotational velocity and acceleration), static conditions are also associated with rotating elements such as pneumatic tiresxe2x80x94for example, pressure and temperature. Failure to correct quickly for improper tire pressure may result in excessive tire wear, blowouts, poor gasoline mileage and steering difficulties. An automatic tire deflation warning system is especially critical for xe2x80x9crun flatxe2x80x9d tires, where the deflated condition is barely detectable by the driver himself. Sensors for static parameters are typically located within the rotating tire, and associated circuitry can transmit data indicative of a sensed condition to an on-board receiver within the vehicle.
Transponder Systems for Pneumatic Tires
A xe2x80x9ctransponderxe2x80x9d is an electronic device capable of both receiving and transmitting radio frequency (RF) signals. Transponder systems, typically including a plurality of transponders and a single interrogator are well known and disclosed, for example, in U.S. Pat. No. 5,339,073, incorporated in its entirety by reference herein.
It is known to put transponders (and associated sensors) in pneumatic tires of motor vehicles. These transponders transmit a RF wave, with or without variable data (e.g., tire pressure, temperature, position) and/or fixed data (e.g., tire ID) to outside the tire, and receive RF signals, with or without data, from outside the tire. A separate transponder is typically associated with each tire of a motor vehicle to monitor and transmit tire-related data. Typically, an xe2x80x9cinterrogatorxe2x80x9d having both transmitting and receiving capabilities is used to communicate with the transponders. The interrogator may be xe2x80x9chand-heldxe2x80x9d, or mounted xe2x80x9con-boardxe2x80x9d the vehicle, or positioned along or in a roadway (e.g., xe2x80x9cdrive-overxe2x80x9d, or xe2x80x9cdrive by xe2x80x9d).
xe2x80x9cActivexe2x80x9d transponders have their own power supply (e.g., a battery). They transmit signals, and are typically also capable of receiving signals to control their functionality.
xe2x80x9cPassivexe2x80x9d transponders are powered by the energy of an incoming RF signal, such as from an interrogator. Passive transponders fall into two general categories, those having only passive circuitry, and those having some active circuitry. In the main, transponders which are passive transponders having some active circuitry are discussed herein.
U.S. Pat. No. 5,612,671, incorporated in its entirety by reference herein, discloses a low tire pressure warning system having a pressure sensor and radio transmitter in each wheel, and a vehicle-mounted receiver including a microprocessor.
U.S. Pat. No. 4,609,905, incorporated in its entirety by reference herein, discloses a passive transponder having only passive circuitry. An RF transmitter in the vehicle interrogates the transponder, which reflects a predetermined harmonic of the RF signal back to a receiver as a function of the state of an associated pressure switch.
U.S. Pat. No. 4,067,235, incorporated in its entirety by reference herein, discloses a passive transponder with a tire pressure sensor. Electromagnetic radiation generated by a power transmitter is received by a receiving antenna comprising an inductor and a capacitor in the tire pressure sensor. This radiation is converted by a rectifier-filter to electricity to power active components (oscillator, buffer amplifier, transmitter) of the transponder.
U.S. Pat. No. 4,724,427, incorporated in its entirety by reference herein, discloses a passive transponder that receives a carrier signal from an interrogator. The carrier signal is rectified by a rectifying circuit connected across the transponder""s antenna coil to generate electricity to power the transponder. Data is encoded and mixed with the carrier signal in a balanced modulator circuit. The output of the balanced modulator circuit is transmitted back to the interrogator unit.
U.S. Pat. No. 4,703,650, incorporated in its entirety by reference herein, discloses a circuit suitable for one of many methods of coding for transmission the values of variables measured in a tire, and a device for monitoring tires employing such a circuit. An astable multivibrator transforms the measurement of the variable in question, for instance pressure and temperature, into a time measurement. The astable multivibrator delivers a pulse signal whose pulse width is a function of the temperature and the cyclic ratio of which is a function of the pressure. The signal is suitably transmitted from the tire to the vehicle by, for example, inductive coupling.
U.S. Pat. No. 4,730,188, incorporated in its entirety by reference herein, discloses a passive transponder excited by an inductive coupling from an interrogator. The transponder responds to the interrogator via the inductive coupling with a signal constituting a stream of data. The transponder comprises an induction coil serving as its antenna, and a full wave rectifier bridge and smoothing capacitor connected across the antenna to provide DC voltage (power) to active circuitry within the transponder.
U.S. Pat. No. 5,969,239, incorporated in its entirety by reference herein, discloses some forms of antennas for electromagnetically coupling moving transponders in tires to stationary antennas on the vehicle. The patent concerns replacing an annular coil type of rotating antenna with a smaller antenna integrated with the measurement sensor (transponder) in one small box firmly attached to the wheel, plus a closed circular strip-iron coupling ring attached to and coaxial with the wheel. The rotating antenna, stationary antenna and coupling ring are positioned so that electric current is induced in the coupling ring by magnetic flow in either of the antennas and vice versa. Alternate embodiments are mentioned which consider using the xe2x80x9cmetallic environmentxe2x80x9d in place of the ring of strip iron, for example the wheel itself, or at least one of the metallic beads of the tire. The frequency of transmission is from 30 to 100 kilohertz.
U.S. Pat. No. 5,824,891, incorporated in its entirety by reference herein, discloses xe2x80x9ca transmitting circuit . . . mounted on a frame member. The transmitting circuit includes a transmitting coil and generates electrical energy . . . .xe2x80x9d A xe2x80x9creceiving is inductively coupled to the transmitting circuit. The receiving circuit includes a sensor for generating a data corresponding to a physical characteristic of the vehicle wheel and a wireless communication circuit for receiving the electrical energy from the transmitting coil to remotely power the receiving circuit and for transferring the data signal from the receiving circuit to the transmitting circuitxe2x80x9d.
U.S. Pat. No. 4,911,217, incorporated in its entirety by reference herein, discloses an RF transponder in a pneumatic tire. FIG. 1a illustrates a prior-art identification system (xe2x80x9creaderxe2x80x9d) that can be used to interrogate and power the transponder within the tire. A portable hand-held module has within it an exciter and circuitry for indicating the numerical identification of the tire/transponder.
U.S. Pat. Nos. 5,181,975 and 5,218,861, incorporated in their entirety by reference herein, disclose a pneumatic tire having an integrated circuit passive transponder located within the structure of the tire for use in tire identification and pressure data transmission. The interrogation signal is rectified by circuitry in the transponder, which then utilizes the rectified signal as its source of electrical power for use in its transmission of digitally encoded signals.
U.S. Pat. No. 4,220,907, incorporated in its entirety by reference herein, discloses a low tire pressure alarm system for vehicles. Each wheel is provided with a transmitter, and there is a common receiver comprising a suitable antenna such as a ferrite loopstick.
U.S. Pat. No. 4,319,220, incorporated in its entirety by reference herein, discloses a system for monitoring tire pressure, comprising wheel units in the tires and a common receiver. Each wheel unit has an antenna comprising a continuous wire loop disposed against the inner periphery of the tire for transmitting signals and for receiving power. Multiple antennas may be provided for the receiver, and may be in the form of ferrite loopsticks.
U.S. Pat. No. 5,319,354, incorporated in its entirety by reference herein, discloses an antenna structure for communicating with an electronic tag (transponder) implanted in a pneumatic tire. This patent recognizes that the orientation of the transponder with respect to the antenna communicating with the transponder can adversely affect coupling between the interrogation antenna and the transponder antenna. A construction of an interrogation antenna is described so that, regardless of the position of the transponder in the pneumatic tire, a position of which is unknown, the coupling is always of the same quality.
The following U.S. Pat. Nos. are also cited as being of interest: 3,835,451, 4,755,345, 5,095,309, 5,235,326, 5,537,867, 5,559,507, 5,594,448, 5,731,754, 5,790,016, 5,790,016, 5,824,891, and 5,826,207, all of which are incorporated in their entirety by reference herein.
International Publication No. WO 99/52722 (Oct. 21, 1999), incorporated in its entirety by reference herein, discloses a method and apparatus for sensing tire pressure in a vehicle wheel which is wireless. It employs xe2x80x9cknownxe2x80x9d pressure and temperature sensors, xe2x80x9cknownxe2x80x9d revolution detectors (e.g., ABS), and xe2x80x9cknownxe2x80x9d controllers. A transducer, the sensors, a power source (e.g., battery), and a transmitter are mounted on the wheel rim, interior to the tire. The transducer measures a pneumatic pressure and/or temperature and/or wheel speed that is converted into a wireless data signal by the transmitter. A receiver coil [antenna] is connected to a portion of the vehicle, such as a wheel well member, preferably within three tenths of a meter of the transducer/transmitter coil. Another coil connected to the vehicle may be tuned to receive wheel speed signals from the xe2x80x9cknown typexe2x80x9d of wheel speed sensor, and these signals are conditioned by the receiver and passed to the controller along with the pressure and temperature signal. The pressure/temperature signal and the wheel speed signal may be distinguished by various known means such as by frequency or modulation design, or a separate receiver can be utilized.
Tire Pressure Regulation
In addition to sensing, if not measuring/monitoring, pneumatic tire pressure, a variety of systems have been developed to regulate, adjust and/or replenish the pneumatic medium (air) in a tire.
U.S. Pat. No. 5,505,080, incorporated in its entirety by reference herein, discloses a tire pressure management system including a tire condition monitor connected to the tire so as to be interactive with air pressure in the tire for selectively measuring a pressure in the tire, a controller, and a display. The tire condition monitor includes a transmitter and a receiver. The controller also has a transmitter and a receiver connected thereto, and the condition monitor and controller communicate via radio signals. An air compressor is mounted to a wheel of the tire so as to deliver air to an interior of the tire when the pressure of the tire is below a predetermined value. A power generator is connected to the wheel of the tire and includes an alternator magnet assembly and an induction coil assembly which are connected to the wheel of the tire such that relative rotation occurs therebetween as the tire rotates. FIG. 7 illustrates a tire pressure sensor, a temperature sensor, and a pick-up coil for revolution counting, all connected to the microprocessor chip of the condition monitor. The revolution counter is said to be usable xe2x80x9cin place of [a] hubometer.xe2x80x9d
U.S. Pat. No. 5,667,606, (referred to hereinbelow as the xe2x80x9cRenier/Cycloid ""606 Patentxe2x80x9d) incorporated in its entirety by reference herein, discloses a tire pressurizing and regulating apparatus comprising a displacement type air pump axially mounted on a vehicle wheel with an air pressure connection conduit introducing air under pressure generated from the pump into the pneumatic tire. A conventional [mechanical] pressure level mechanism is also provided and connected to the pump for establishing and maintaining a desired air pressure in the tire at a predetermined level. A cam and cam follower arrangement is mounted in the housing for the pump, and a pendulum is mounted for free axial rotation relative to the pump housing. The pendulum is connected to one of the cam or cam follower, and the other is secured to the pump housing for rotation therewith to provide a cam actuated driving movement for the pump.
U.S. Pat. No. 4,742,857, incorporated in its entirety by reference herein, discloses a tire pressure sensor and air supply to maintain desired tire pressure. The disclosed system for detecting the air pressure in each wheel (by means of a moveable magnet pressure sensor) and for effecting inflation or deflation in each wheel (by means of a valve connected to the moveable magnet) while the vehicle is operating, includes a controller and a high pressure reservoir mounted on each wheel. A data processor displays the tire pressure to the vehicle operator and allows for manual actuation of the valve for raising or lowering of the tire pressure.
U.S. Pat. No. 5,413,159, incorporated in its entirety by reference herein, discloses a self regulating tire pressure system and method which employs a bistable valve that allows air from a high pressure reservoir (mounted on the wheel) to replenish the pressure within a tire when it has fallen below an actuating pressure, and discontinues its operation only after the tire pressure has increased to a closing pressure that is greater than the actuating pressure. The system is capable of sensing the frequency, number and duration of the valve""s operations as indications of a slow tire leak, a flat, or a low reservoir pressure condition, respectively.
In a variation that does not require an air pressure supply mounted on the tire, Brazilian Patent No. PI 9603529-3A, incorporated in its entirety by reference herein, discloses a system with one or more minicompressors with pressure sensors mounted in the vehicle and coupled to the tires by means of rotating air couplings.
According to an aspect of the invention, a system for monitoring pneumatic tire conditions for one or more tire/wheel assemblies mounted on a vehicle, each tire/wheel assembly comprising a tire mounted on a wheel or wheel carrier, is characterized by: a wheel or wheel carrier transponder with a wheel or wheel carrier antenna mounted on the wheel or wheel carrier of the one or more tire/wheel assemblies for transmitting a signal indicating the rotational angular position of the wheel or wheel carrier; one or more receivers each having one or more receiving antennas fixedly mounted on the vehicle, the one or more receiving antennas being positioned to receive the signal from a specific one of the tire/wheel assemblies; and circuitry for processing the signals received by the one or more receiving antennas to determine the rotational angular position of the wheel or wheel carrier of the one or more tire/wheel assemblies.
According to an aspect of the invention, at least one of the wheel or wheel carrier antennas is substantially circular and includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the at least one wheel or wheel carrier antenna for causing blips which are indicative of the rotational angular position of the wheel or wheel carrier antenna to occur in the signal received by the receiving antenna which is positioned to receive the signal from the at least one wheel or wheel carrier antenna.
According to an aspect of the invention, at least one of the wheel or wheel carrier antennas is a conductive hoop coupled to the wheel or wheel carrier transponder; and each conductive hoop wheel or wheel carrier antenna includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the conductive hoop wheel or wheel carrier antenna for causing blips which are indicative of the rotational angular position of the conductive hoop wheel or wheel carrier antenna to occur in the signal received by the receiving antenna which is positioned to receive the signal from the at least one wheel or wheel carrier antenna.
According to an aspect of the invention, a method for monitoring pneumatic tire conditions for one or more tire/wheel assemblies each comprising a tire mounted on a wheel or wheel carrier, is characterized by the step of comparing the rotational angular position of a tire to the rotational angular position of the wheel or wheel carrier in the tire""s tire/wheel assembly in order to determine operating conditions of the tire.
According to an aspect of the invention, the method can include further determining pneumatic tire conditions by monitoring one or more of a tire pressure, a tire temperature, and a count of tire revolutions.
According to an aspect of the invention, the method can include measuring the rotational angular position of a radially outer portion of the tire by means of an RF signal transmitted by an antenna mounted inside the tire near the outer circumference of the tire.
According to another aspect of the invention, a system for monitoring pneumatic tire conditions for one or more tire/wheel assemblies mounted on a vehicle, each tire/wheel assembly comprising a tire mounted on a wheel or wheel carrier, is characterized by: a wheel or wheel carrier transponder with a wheel or wheel carrier antenna mounted on the wheel or wheel carrier of the one or more tire/wheel assemblies for transmitting a first signal indicating the rotational angular position of the wheel or wheel carrier; a tire transponder with a tire antenna mounted on the tire of the one or more tire/wheel assemblies for transmitting a second signal indicating the rotational angular position of the tire; one or more receivers each having one or more receiving antennas fixedly mounted on the vehicle, the one or more receiving antennas being positioned to receive the first signal and the second signal from a specific one of the tire/wheel assemblies; and circuitry for processing the first and second signals received by the one or more receiving antennas to determine the rotational angular position of the tire relative to the wheel of the one or more tire/wheel assemblies.
According to an aspect of the invention, at least one of the tire antennas is substantially circular and includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the at least one tire antenna for causing blips which are indicative of the rotational angular position of the tire antenna to occur in the second signal received by the receiving antenna which is positioned to receive the second signal from the at least one tire antenna. Preferably, the at least one tire antenna which includes a plurality of reactive circuit affecting elements is mounted near the outer circumference of the tire.
According to an aspect of the invention, at least one of the wheel or wheel carrier antennas is substantially circular and includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the at least one wheel or wheel carrier antenna for causing blips which are indicative of the rotational angular position of the wheel or wheel carrier antenna to occur in the first signal received by the receiving antenna which is positioned to receive the first signal from the at least one wheel or wheel carrier antenna.
According to an aspect of the invention, at least one of the tire antennas is a conductive hoop coupled to the tire transponder; and each conductive hoop tire antenna includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the conductive hoop tire antenna for causing blips which are indicative of the rotational angular position of the conductive hoop tire antenna to occur in the second signal received by the receiving antenna which is positioned to receive the second signal from the at least one tire antenna. Preferably, the at least one conductive hoop tire antenna which includes a plurality of reactive circuit affecting elements is mounted near the outer circumference of the tire.
According to an aspect of the invention, at least one of the wheel or wheel carrier antennas is a conductive hoop coupled to the wheel or wheel carrier transponder; and each conductive hoop wheel or wheel carrier antenna includes a plurality of reactive circuit affecting elements incorporated into and spaced about the circumference of the conductive hoop wheel or wheel carrier antenna for causing blips which are indicative of the rotational angular position of the conductive hoop wheel or wheel carrier antenna to occur in the first signal received by the receiving antenna which is positioned to receive the first signal from the at least one wheel or wheel carrier antenna.
According to an aspect of the invention, a sub-receiver is associated with each of the one or more receiving antennas; and the sub-receivers assist a single receiver in processing the signals.
According to an aspect of the invention, there can be one receiving antenna for each specific tire/wheel assembly; and each receiving antenna is configured to receive the first signal at a first frequency from the wheel or wheel carrier antenna of the specific tire/wheel assembly, and is configured to receive the second signal at a second frequency from the tire antenna of the specific tire/wheel assembly. Alternatively, there can be a tire receiving antenna for each specific tire antenna, wherein the tire receiving antenna is positioned by fixedly mounting it on a wheel housing in close proximity to the tire antenna on the tire; and there is a wheel or wheel carrier receiving antenna for each specific wheel or wheel carrier antenna, wherein the wheel or wheel carrier receiving antenna is positioned by fixedly mounting it on an axle housing in close proximity to the wheel or wheel carrier antenna on the wheel or wheel carrier.
According to an aspect of the invention, one or more of the tire transponders and of the wheel or wheel carrier transponders is a passive transponder; and the receiver and receiving antenna associated with each of the one or more passive transponders transmit an interrogating signal to the associated passive transponder.
Other objects, aspects, features and advantages of the invention will become apparent in light of the following description thereof.